Tank fill vapor control

ABSTRACT

A vapor loss control system for a vehicle fuel supply system includes a first vapor recovery circuit from a vapor space of a gas tank to an air purged canister having a first predetermined volume of vapor adsorbing active material; and wherein the outlet of the canister is connected to a ported vacuum connection in a carburetor for selectively purging said first canister during each engine operation at a rate to purge said first canister for subsequent recovery of vapors. The system further includes a second vapor recovery circuit with second larger volume vapor adsorbing canister in communication with a normally closed, unrestricted vent port on the filler neck of the tank which is opened during fuel fill operation to direct tank vapors into the second canister; and wherein means including a flow restrictor communicate the outlet of the second larger volume canister with the intake manifold to produce a rate of recovery of vapors from the second canister sufficient to purge it between tank fill operations without excessive enrichment of fuel flow into the intake manifold.

United States Patent [191 Krautwurst et al.

[ TANK FILL VAPOR CONTROL [75] Inventors: Homer V. Krautwurst; CristianF.

Schulitz, both of Rochester, NY.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

22 Filed: Apr. 15, 1974 21 Appl. No.: 461,010

Primary Examiner-Manuel A. Antonakas Assistant Examiner-James W.Cramson, Jr. Attorney, Agent, or FirmJ. C. Evans [451 May 20, 1975 [57]ABSTRACT A vapor loss control system for a vehicle fuel supply systemincludes a first vapor recovery circuit from a vapor space of a gas tankto an air purged canister having a first predetermined volume of vaporadsorbing active material; and wherein the outlet of the canister isconnected to a ported vacuum connection in a carburetor for selectivelypurging said first canister during each engine operation at a rate topurge said first canister for subsequent recovery of vapors. The systemfurther includes a second vapor recovery circuit with second largervolume vapor adsorbing canister in communication with a normally closed,unrestricted vent port on the filler neck of the tank which is openedduring fuel fill operation to direct tank vapors into the secondcanister; and wherein means including a flow restrictor communicate theoutlet of the second larger volume canister with the intake manifold toproduce a rate of recovery of vapors from the second canister sufficientto purge it between tank fill operations without excessive enrichment offuel flow into the intake manifold.

3 Claims, 3 Drawing Figures PATENTEI] HAY 2 0 I975 SHEET 10? 2 TO FUELPUMP TANK FILL VAPOR CONTROL This invention relates to evaporationcontrol systems for limiting gasoline vapor discharge into theatmosphere from the fuel supply of an internal combustion engine andmore particularly to systems having vapor collection canisters thereinwith active vapor adsorbing material to adsorb and store fuel vapors andmeans for selectively withdrawing the adsorbed fuel vapors forconsumption in the engine combustion process.

Evaporation control systems for collecting vapors from the fuel supplycomponents including the fuel tank and carburetor fuel bowl of aninternal combustion engine include means for adsorbing and storing fuelvapors in a charcoal canister as generated from the fuel bowl duringheat soak periods of engine operation and as generated from the fueltank under elevated ambient temperature conditions. These collectedvapors are drawn from the canister when the engine is running andsubsequently consumed in the engine combustion process. Typically, suchsystems connect the canister to a source of vacuum in the intake fuelsupply system of the vehicle which is used to draw the collected vaporsfrom the canister at a rate that will serve to purge the active materialof canister adsorbed vapors during each engine operation to conditionthe canister for collection of subsequently generated vapors The purgerate is selected to prevent excessive enrichment of a predeterminedair-fuel supply from a carburetor to the intake manifold of the engine.

Such systems are satisfactory for their intended purpose undercircumstances where fuel vapors are directed out the filler neck of agas tank directly to atmosphere when the tank is being filled with fuel.In order to improve vapor collection, it has been proposed that thefiller neck be sealed during the fill phase of operation and that fillgenerated vapors be directed to an evaporative control canister. Thus,the canister must adsorb substantially greater volumes of vapor eachtime that the tank is filled. In order to effectively purge the canisterin such systems, the purge rate must be elevated in order to purge bothdaily adsorption of fuel vapor emissions from the fuel tank and the fuelbowl and the added charge of fill generated vapors. Such purge rates canaffect engine operation or increase engine exhaust emissions of unburnedhydrocarbons or both.

Accordingly, it is an object of the present invention to improvecollection of fuel vapor emissions from a vehicle fuel supply system bythe provision of first canister means having an inlet for collection ofvapors generated during daily vehicle operation from a fuel tank andcarburetor bowl and wherein means are provided to purge vapors from thefirst canister means for consumption in the engine at a rate tocondition the first canister means for collection of subsequentlygenerated vapors; and by the further provision of second canister meansconnected to the fuel tank by means for collection of vapors generatedduring gas tank fill operations without affecting the cycle ofcollection and purge of vapors from the first canister means; andwherein the second canister means is connected to means for purging suchvapors at a reduced rate into the intake manifold of the engine to avoidadverse engine operation or production of increased exhaust emissions ofunburned hydrocarbons.

Another object of the present invention is to provide an improved twocanister evaporative emission control system for collecting fuel vaporsfrom a fuel supply system for the vehicle including a first smallcapacity canister operative to collect vapors generated within a fueltank and from a fuel bowl of the carburetor during engine operation andincluding means for purging collected vapors from the small capacitycanister during each engine operation to condition the canister forsubsequent collection of vapors generated from the tank and carburetorbowl and wherein means are provided to direct vapors from the tank intoa second larger volume canister during a fuel fill phase of operationwithout passage of additional vapors into the smaller canister withmeans being provided to purge the larger volume canister into the intakemanifold of an engine at a lesser rate than the purge rate from thefirst canister to avoid adverse engine operation or increased exhaustemission of unburned hydrocarbons from the engine during its operation.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

IN THE DRAWINGS FIG. 1 is a diagrammatic view of an evaporative losscontrol system including two vapor collection canisters in accordancewith the present invention;

FIG. 2 is a view in vertical section taken along the line 22 of FIG. 1looking in the direction of the arrows; and

FIG. 3 is an enlarged fragmentary sectional view of a sealed fuel fillerneck used in the present invention.

Referring now to the drawings, in FIG. 1 a fuel tank 10 is illustratedhaving a dome 12 thereon defining an interior fuel air vapor space 14,in which fuel vapors generated during vehicle operation are collected. Avent conduit 16 from the space 14 is connected across an orifice 17 tothe inlet 18 of a reduced volume fuel vapor collection canister 20 sizedto be located easily within the engine compartment of a vehicle. Thecanister 20 is of a conventional configuration having an interior volume22 filled in part with an active vapor adsorbing material 24 such asactivated charcoal or carbon. The canister 20 includes a purge fitting26 to the interior volume 22 and in communication with air ambient thecanister 20. The canister 20 further includes an outlet 28 therefromcommunicated across a restrictor 30 to a vapor conduit 32 that isconnected to a ported vacuum source defined by first and second ports34, 36 located within a bore 38 of a carburetor 40 for supplying apredetermined air-fuel ratio to the intake manifold 41 of an internalcombustion engine. The bore 38 includes a throttle valve 42 thereinwhich, when positioned in an idle position, as illustrated in FIG'. 1,is located below the port 34 and above the port therein such asactivated charcoal or carbon and includes an inlet 54 at one end thereofand an air purge connection 56 at the opposite end thereof incommunication with air ambient the canister 46 at the rear of thevehicle. The canister 46 further includes an outlet 58 connected by apurge conduit 60 across a restrictor 62 to a carburetor port 64 belowthrottle valve 42 to be exposed to the intake manifold pressure of thevehicle. A vent conduit 65 communicates the carburetor fuel bowl 66 withthe canister 20 during engine soak conditions.

In the illustrated arrangement, the inlet 54 to the large volumecanister 46 is connected by an intake con duit 67 to a side fitting 68on the end of a filler neck 70. A vent port 72 is located in the fillerneck 70 to communicate the fitting 68 with the interior thereof at apoint adjacent the upper open end 74 of the filler neck.

A seal cap assembly 76 is located on the open end 74 of the filler neckand includes a gasket 78 to seal the end of neck 70. The cap 76 which isrepresentatively shown as a cap that is suitable for association withthe system of the present invention is illustrated with adiagrammatically shown seal 80 thereon that coacts with an internallylocated reduced diameter 82 on the filler neck 70 interiorly thereoflocated between the open end 74 of the filler neck and the interior ofthe tank to seal the vent port 72 when the cap 76 is in place on thefiller neck 70. Accordingly, vapor flow from the tank 10 is maintainedthrough the small capacity canister during normal vehicle operation andthe vent port 72 is only open when the cap 76 is removed from the fillerneck 70.

As shown in FIG. 3, a fuel fill nozzle 84 is positioned in the open end74 during a fill phase of operation with the seal cap 76 removed fromthe filler neck 70. A suitable seal component such as a bellows 86 isconnected between the nozzle 84 and the filler neck 70 to completelyseal the system during this phase of operation. Accordingly, fuel vaporsthat are directed into the tank 10 during fill from nozzle 84 aredirected through the unrestricted port 72 rather than the restrictedvent 16 from the vapor space 14 of the tank 10 so that vapors areaccumulated in the larger volume of the canister 46 during the filloperation. During this period of time, only a limited flow of vaporswill pass into the canister 20 so that the vapor adsorbing capacity ofthe charcoal material 24 therein will not be overloaded with vaporsduring the fill phase of operation. The volume of the activated charcoal52 in the large volume canister 46 is selected to accommodate the largevolume vapors produced during the tank fill of operation. Once the sealcap 76 is in place on the filler neck 70, the larger rear canister 46 ispurged to remove the vapor therefrom at a rate which removes adsorbedvapor from the rear canister so as to accommodate vapors produced duringa subsequent tank fill cycle of operation. This period of time is of aduration to permit a reduced purge rate as compared to the purge ratefrom the canister 20 so that the vapors drawn through the port 64 willnot adversely effect exhaust emissions from the engine. The two canistersystem is better than a single large canister located in the front ofthe vehicle which has to be purged at increased rates to accommodateboth fill generated vapors and engine operation generated vapors. Suchrates can adversely affect the exhaust emission levels from the engine.

An additional advantage of the rear mounting of the canister 46 is thatvibrational forces on the canister 46 are reduced enabling it to beconstructed of a less expensive plastic material than high strengthplastic such as nylon 66 as required for the front canister.

While the embodiments of the present invention, as herein disclosed,constitute a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is:

1. In an internal combustion engine, an evaporation control system forlimiting vapor loss from a fuel supply including a fuel tank having avapor space and an airfuel supply carburetor for directing apredetermined fuel charge into the intake manifold of an internalcombustion engine comprising: means for adsorbing vapor generated fromthe tank during normal vehicle operation including a first canistermeans having a first predetermined volume, means for communicating theinterior of said first canister means with an engine carburetor forpurging vapor from said first canister means during engine operation forconsumption in the engine, second vapor adsorbing means for adsorbingvapors produced within said tank during a fill phase of operationincluding second canister means having a second predetermined volumegreater than said first predetermined volume to adsorb increased volumeof vapors produced during tank fill operation, and means for purgingvapors from said second canister means for consumption with the engineduring engine operation at a lesser rate than the rate of withdrawal ofvapors from said first canister means thereby to avoid excessiveenrichment of the air-fuel mixture to the intake manifold of theinternal combustion engine so as to prevent excessive exhaust emissionstherefrom.

2. In an internal combustion engine, an evaporation control system tolimit vapor loss from a fuel tank comprising: a vent space within saidtank having a vent thereon, a first canister having a firstpredetermined volume therein filled with vapor adsorbing material, saidfirst canister having a purge connection thereto in communication withair ambient said first canister and including an inlet and outlettherefrom located on the opposite end of said canister from said purgeconnection, means communicating the inlet of said first canister withsaid vent, carburetor means for supplying a predetermined air-fuel ratioto the intake manifold of the vehicle including a bore therethroughhaving a throttle valve therein, port means located within said bore atpoints above and below said throttle valve under idle conditions, meansfor communicating the outlet of said first canister with said carburetorport means including a restriction for establishing a predetermined rateof purge through said first canister during engine operations towithdraw vapors from said first canister for passage through saidcarburetor bore into the engine for consumption therein, saidrestriction controlling flow of vapors from said first canister at arate to prevent excessive enrichment of the air-fuel ratio to the engineduring operation thereof, a second canister having a volume thereinfilled with vapor adsorbing material greater than said firstpredetermined volume, said second canister including an inlet and outleton one end thereof and a purge connection on the opposite end thereof, afill neck on said tank having an unrestricted vent port thereon at oneend thereof, seal cap means on said filler neck for blockingcommunication between said unrestricted vent port and the interior ofsaid tank following a tank fuel fill operation, a supply conduit forcommunicating the unrestricted vent port with the inlet to said secondcanister, said unrestricted vent port being opened during a sealed tankfuel fill operation and having vapors from said tank directedtherethrough for adsorption on said greater volume of adsorbing materialin said second canister, and means for connecting the outlet of saidsecond canister with engine intake manifold vacuum including arestrictor having a reduced flow area to cause vapors to be purged fromsaid second canister at a rate reduced from that of the purge rate fromsaid first canister to prevent excessive flow of vapor into the intakemaniduring the fill phase of operation.

1. In an internal combustion engine, an evaporation control system forlimiting vapor loss from a fuel supply including a fuel tank having avapor space and an air-fuel supply carburetor for directing apredetermined fuel charge into the intake manifold of an internalcombustion engine comprising: means for adsorbing vapor generated fromthe tank during normal vehicle operation including a first canistermeans having a first predetermined volume, means for communicating theinterior of said first canister means with an engine carburetor forpurging vapor from said first canister means during engine operation forconsumption in the engine, second vapor adsorbing means for adsorbingvapors produced within said tank during a fill phase of operationincluding second canister means having a second predetermined volumegreater than said first predetermined volume to adsorb increased volumeof vapors produced during tank fill operation, and means for purgingvapors from said second canister means for consumption with the engineduring engine operation at a lesser rate than the rate of withdrawal ofvapors from said first canister means thereby to avoid excessiveenrichment of the air-fuel mixture to the intake manifold of theinternal combustion engine so as to prevent excessive exhaust emissionstherefrom.
 2. In an internal combustion engine, an evaporation controlsystem to limit vapor loss from a fuel tank comprising: a vent spacewithin said tank having a vent thereon, a first canister having a firstpredetermined volume therein filled with vapor adsorbing material, saidfirst canister having a purge connection thereto in communication withair ambient said first canister and including an inlet and outlettherefrom located on the opposite end of said canister from said purgeconnection, means communicating the inlet of said first canister withsaid vent, carburetor means for supplying a predetermined air-fuel ratioto the intake manifold of the vehicle including a bore therethroughhaving a throttle valve therein, port means located within said bore atpoints above and below said throttle valve under idle conditions, meansfor communicating the outlet of said first canister with said carburetorport means including a restriction for establishing a predetermined rateof purge through said first canister during engine operations towithdraw vapors from said first canister for passage through saidcarburetor bore into the engine for consumption therein, saidrestriction controlling flow of vapors from said first canister at arate to prevent excessive enrichment of the air-fuel ratio to the engineduring operation thereof, a second canister having a volume thereinfilled with vapor adsorbing material greater than said firstpredetermined volume, said second canister including an inlet and outleton one end thereof and a purge connection on the opposite end thereof, afill neck on said tank having an unrestricted vent port thereon at oneend thereof, seal cap means on said filler neck for blockingcommunication between said unrestricted vent port and the interior ofsaid tank following a tank fuel fill operation, a supply conduit forcommunicating the unrestricted vent port with the inlet to said secondcanister, said unrestricted vent port being opened during a sealed tankfuel fill operation and having vapors from said tank directedtherethrough for adsorption on said greater volume of adsorbing materialin said second canister, and means for connecting the outlet of saidsecond canister with engine intake manifold vacuum including arestrictor having a reduced flow area to cause vapOrs to be purged fromsaid second canister at a rate reduced from that of the purge rate fromsaid first canister to prevent excessive flow of vapor into the intakemanifold of the engine and a resultant increase in engine emissions. 3.In the combination of claim 2, said tank having a horizontal uppersurface, said second canister being supported on the horizonal uppersurface of said tank and having the inlet end thereof located closelyadjacent said filler neck and said vent port on said filler neck toreduce the length of said supply conduit from said vapor port to saidsecond canister inlet so as to improve flow of vapors from said tankinto said second canister for adsorption on the active material thereinduring the fill phase of operation.